1973 Undersea fault near Diablo Canyon

November 22, 2008 – 8:00 am

November 24, 1973

Time gets measured in different scales. Geologic time runs in cycles with spans of hundreds, thousands or millions of years, hard to put in a human context because the Earth’s pace is not a human pace.
A few signposts of 1973: Richard Nixon was president, and the jaws of the Watergate scandal were closing on him. Telegram-Tribune cost 15 cents and did not have a Sunday edition. Graphics were drawn by hand then photographed, not created on a computer. Thrifty was the name of a drug store. The nuclear power industry answered to the Atomic Energy Commission.
Almost exactly 35 years ago the discovery of what would undersea fault a mile off the coast was reported in the then Telegram-Tribune.
The United States Geological Survey and the AEC had commissioned a study of the seabed off of Diablo Canyon after scientist Gary Greene had discovered an active fault offshore from Davenport in Santa Cruz. PG&E dropped plans to build a nuclear power there in the wake of that report.
Staff writer Jim Hayes quoted Greene:
“Of course, PG&E had other problems there. There was the fault at Ano Nuevo and then they had a landslide.”
Later in the article the scientist spoke about the newly discovered fault,
“Length, becomes a critical factor, generally the longer the fault the more recent and active we think it is.”
A PG&E spokesman Frederick R. Draeger downplayed the discovery saying Diablo Canyon had been designed “to handle the greatest earthquake that could occur.”
In 1973 both units of the plant were expected to open within two years and the price tag stood at $650 million dollars. Both numbers would balloon as the plant was retrofitted in the wake of the discovery.

Today David Sneed has an article on a fault discovered about a mile offshore from the plant.

2 Responses to “1973 Undersea fault near Diablo Canyon”
The scarp I wrote about 35 years ago was one mile offshore. The Hosgri now is described as being three miles offshore. Isn’t it likely that the scarp was related to the “new” fault?

By Jim Hayes on Nov 22, 2008
Thanks for the comment Jim.
For those of you that don’t know Jim Hayes is a former Telegram-Tribune staff writer and section editor. He is a writing coach who’s clients have included papers as small as The Tribune and as large as the Los Angeles Times. When I first met him he was teaching the best writing class I ever had at Cal Poly. I’m lucky this post did not come back with a red mark “F - Hayes”.
A deeper look at the files turns up a September 12, 1981 timeline that shows a more complex relationship to the Hosgri Fault. The post above has been edited and the newer information follows.

Nov. 24 1973: An undersea scarp-a 10-foot-high displacement that could have been caused by an earthquake fault-is reported by U.S. Geological Survey researchers about a mile offshore of Diablo Canyon.
Geologist Gary Greene, of the USGS research vessel George B. Kelz, which mapped the scarp, said the trace extends several miles along he ocean floor paralell to the coastline. He said the fault could be active.
PG&E nuclear information specialist Frederick R. “Fritz” Draeger says the Diablo plant was designed “to handle the greatest earthquake that could occur.”

Dec. 17, 1973: U.S. Geological Survey geologist Holly Wagner confirms a fault has been found offshore of the Diablo Canyon nuclear power plant. It turns out not to be the scarp originally identified by survey researchers but another structure 3 miles offshore. The scarp proved to be a marine terrace.
Wagner later finds out that the fault was discovered in 1969 and mapped in a 1971 paper by two Shell Oil geologists, Ernest G. Hoskins and John R. Griffith, who had done a survey on offshore oil deposits. Taking the first three letters of each of their last names, Wagner names it the Hosgri Fault.

It could be the structure that was called a fault or marine terrace a mile offshore in 1973 is the same fault reported in about the same location on Saturday.

Thanks for the assist in my continuing education Jim.

By David Middlecamp on Nov 24, 2008